Lecture 1.1b - Cell injury and cell death 1.pdf

Necrosis: ◦Defined as the morphological changes that occur in a living organism after a cell has been dead for some time (non-programmable cell death) ◦Seen after 12-24 hours ◦Oncosis - cell death with swelling, the spectrum of changes that occur in injured cells prior to death T...

Necrosis: ◦Defined as the morphological changes that occur in a living organism after a cell has been dead for some time (non-programmable cell death) ◦Seen after 12-24 hours ◦Oncosis - cell death with swelling, the spectrum of changes that occur in injured cells prior to death Types of necrosis: ◦Two main types: ‣ Coagulative ‣ Liquefactive (colliquitive) ◦Two other special types: ‣ Caseous ‣ Fat necrosis Why are there two types of necrosis?: What does coagulative necrosis look like?: ◦Denaturation of proteins dominates over release of active proteases ◦Cellular architecture is somewhat preserved, “ghost outline” of cells Liquefactive necrosis:  ◦Complete dissolution of necrotic tissue ◦Most commonly due to massive infiltration by neutrophils (abscess formation) ◦Release of reactive oxygen species and proteases ◦Enzyme degradation is substantially greater than denaturation ◦Leads to enzymatic digestion (liquefaction) of tissues What is caseous necrosis?: ◦Contains amorphous (structureless) debris (ghost outline in coagulative necrosis) ◦Particularly associated with infections, especially tuberculosis What does caseous necrosis look like?: What is fat necrosis and what does it look like?: ◦Results from the action of lipases released into adipose tissue. ◦Free fatty acids accumulate and precipitate as calcium soaps (saponification) ◦These precipitates are grossly visible as pale yellow/white nodules